The artificial leather is used for various purposes because of having texture and tactility similar to those of the natural leather, and natural exterior appearance. The artificial leather is mainly manufactured by a method of coating polymer resin on fiber sheet, and used for various purposes such as vehicular interior materials, sofa materials for furniture, interior materials, and shoe upper materials. Particularly, the artificial leather is used recently for various usages including interior materials for railroad trains, interior materials for air planes and interior materials for ships.
The artificial leather is mostly comprised of PVC (Polyvinyl Chloride), or PU (Polyurethane), and formed with a skin layer, an adhesive layer and a base layer. The PU artificial leather is generally used with a resin mixed with a solid PU, a DMF (Dimethyleformamide) or an MEK (Methyl Ethyl Ketone). The PU artificial leather is manufactured by forming a thin film after being coated with a non-woven fabric, by mixing an additional pyroxene solvent to the resin according to the usages. When PU used for PU artificial leather is mixed with DMF, the PU artificial leather may be manufacture by using a wet process, and when the MEK is mixed, the PU artificial leather may be manufactured by using a dry process. The wet process is such that a solution mixed with PU, DMF and additive is impregnated on a raw fabric such as non-woven fabric, coated with PU mixed liquid, deposited in a coagulation bath of water and DMF mixed liquid under 30° C., and a finely porous film can be formed by substitution reaction of water and DMF. The dry process is a manufacturing method in which a mixed solution of PU resin, MEK and DMF resin is coated on a release sheet engraved with a pattern, dried with hot wind, formed with film, and adhered on a support fabric.
However, the PU artificial leather thus described suffers from disadvantages in that environmental problems arise in the manufacturing process because of using an excessive amount of organic solution and residual harmful materials (VOCs, Volatile Organic Compounds) is detected when an artificial leather is manufactured, and therefore, its use is limited. Particularly, when the PU artificial leather is used for vehicular interior materials or airplane interior materials, generation of cyanide gas during combustion, which is a toxic gas, results in problems of safety for passengers, and environmental problems are also generated during disposal.
The manufacturing method of PVC artificial leather may be categorized into two ways, that is, a calendar method in which PVC polymer is mixed, using a mixer, with a mixed solid including plasticizer, pigment, processing material and additive, and sheeted using a calendar, and a casting method in which a release sheet engraved with a pattern is coated with a mixed solution, and filmed. A sheeted PVC product thus manufactured is bonded with fabric, and surface-treated with embossed expressions.
Various types of PVC artificial leather is widely used for various usages because of being excellent in processibility and low price. However, when the PVC artificial leather is used for a long time, problems in terms of physical properties such as film peeling and generation of VOC are disadvantageously generated. Furthermore, the PVC artificial leather is used with plasticizer for softness and processibility, and the plasticizer generates an environmental hormone, a harmful material known as DEHP (Di-2 ethylhexylphtalate), and therefore, its use is strictly restricted by advanced countries in Europe and USA and by domestic car manufacturers as well. In order to solve the problems of artificial leather, waterborne PU artificial leather and high solid PU artificial leather products have been proposed, but other problems such as quality stability, limitation in physical properties, increase in price and recycling after use have emerged.